Question

Lichens are used as pollution indicators because ___________.

• A. they grow only in polluted areas
• B. they do not grow in polluted areas
• C. they change colour when they come in contact with pollutants
• D. Both a and c

Answer 1

The correct option is B they do not grow in polluted areas

Lichens are symbiotic associations between a fungal component (mycobiont) and an algal component (phycobiont).

The algae is the photosynthetic producer which prepares food and shares it with the heterotrophic (consumer) fungal component.

The fungal component in return provides shelter to the algal component and also absorbs water and minerals.

Lichens are important pollution indicators because they do not grow in areas where the air is highly polluted. So the growth of lichens indicates that the level of pollution in the area is very less. If the air is very badly polluted with sulphur dioxide there may be no lichens present, just green algae may be found. Hence option b is correct and option a is incorrect.

Lichens do not show any colour change on coming in contact with pollutants. Hence option c is incorrect.

Three types of lichens present, they are the Crustose (crusty), Foliose (leafy) and Fruticose (bushy) lichens.

Figure : Lichen as pollution indicator